72,476 research outputs found
Hawaii Deep Water Cable Program phase II : cable construction specification
No full textThis document constitutes a detailed construction specification covering the design, fabrication and testing of the preferred 250 MW dc self contained oil filled (SCOF) cable to be used for the laboratory and possibly at-sea portions of the U.S. Department of Energy Hawaii Deep Water Cable (HDWC) Program. All cable materials, components, details of cable fabrication and test requirements are fully described. This specification incorporates a level of technical detail sufficient to permit an experience cable manufacturer to produce a length of cable
Hawaii Deep Water Cable Program, phase II : laboratory test protocol
No full textThe objective of the laboratory test program is to demonstrate that the selected cable and joints are capable of withstanding the expected mechanical stresses and environmental conditions to be encountered during deployment, retrieval and in operation while retaining the electrical characteristics necessary for a service life exceeding 30 years. In addition, the objective is to obtain data to optimize the final cable system design. Routine and Type (Qualification) Tests, based on Electra No. 68 and No. 72, will be performed by the manufacturer on full cable lengths or on sample cable lengths, as applicable, from the same production lot as will be used for the laboratory test program. A detailed description of the qualification tests is included in Appendix A for
reference purposes
Hawaii Deep Water Cable (HDWC) Program : cable overloadability study
No full textThe scope of this study is to determine the short term overload capability of Cable No. 116 in the event of the loss of one pole of the dc transmission system. Such a loss would result in the loss of 250 MW of transmitted power. This exceeds the spinning reserve capability of the Hawaiian Electric Company on Oahu. The maximum allowable first contingency power loss which can be accomodated by the available spinning reserve while maintaining the integrity of the system is 125 MW. The loss of one pole of the dc system would therefore require an increase of 50 percent in the transmitted power on the remaining pole for a period of time up to 4 hours. The surviving pole conductor during this period must therefore carry 150 percent of rated power, i.e. 375 MW corresponding to 1250 amps. The findings are included in this report
Dynamics Simulation of Remotely Operated Vehicle-Fiber Optic Micro Cable System
No full textLi Q, Xu H, Zhang Q, Wang X, Li ZG. Dynamics Simulation of Remotely Operated Vehicle-Fiber Optic Micro Cable System. Presented at the WCICA2008, Chongqing, China
Rating methodology of high voltage mass impregnated DC cable circuits
No full textWith the continuing growth in energy consumption worldwide, the move towards a European wide super grid will result in significant changes in how modern transmission and distribution networks are operated. Fundamental to this is the need to accurately know or determine the available ampacity of high voltage cable circuits, because huge bulk power volumes need to be transmitted between maritime nations through dc power cables. Therefore, an accurate cable rating becomes paramount towards an efficient and safe operation of transmission networks, while the finance for large scale network construction schemes is limited.Although the standardised thermal-limited rating has been successfully implemented for traditional ac cable networks for over 50 years, the move towards dc cable transmission imposes extra physical constraints on the cable rating, which are not considered by standard rating approaches. The two main concerns are the potential dielectric electrical breakdown prior to a normal thermal runaway and the development of dielectric cavities during cable cooling. In addition, the thermal-limited rating of submarine dc cable crossings, within a complex marine environment, requires an advanced numerical modelling method, where the traditional IEC thermal-limited rating method does not apply. Besides the technical value, significant interest exists both within the electrical power industry and organizations such as Cigré and IEC, because this work will inform future international standards for rating high voltage dc cables.Considering the dielectric electrical stress constraint as the limiting factor for cable ratings, an analytical electrical stress-limited rating method has been developed and successfully benchmarked by numerical simulations for a practical cable design. This method allows ratings to be calculated against a criterion of maximum dielectric electrical strength.Considering the dielectric cavity creation threshold as the limiting factor for cable ratings, a comprehensive study has been conducted, including thermal dynamics, theory of elasticity and electrical circuit theory. Subsequently, the analytical calculation of the cable internal pressure has been originally developed, together with a concept of the mechanical pressure-limited rating. The method has been successfully demonstrated for a practical cable design, yielding a rating which prevents the creation of cavity due to potential plastic deformations of the cable sheath.When crossings are inevitably installed, cables are pushed towards their thermal limit, as a result of the mutual heating. In order to accurately rate these circuits under various ambient conditions; Finite Element Analysis (FEA) methods have been developed. Compared to the traditional IEC calculation, FEA modelling provides a more reasonable and accurate solution, by releasing idealistic assumptions in the IEC method. In addition, a systematic cable rating strategy has been suggested and successfully demonstrated through rating submarine high voltage dc cable crossings, which considers highly coupled physics: thermal, electrical and mechanical. In summary, this thesis contributes towards the modern rating methodology development for hvdc mass impregnated cable circuits, under a purpose of efficient and reliable long-term operation
Wind loads analysis at the anchorages of the Talavera de la Reina cable stayed bridge
No full textThis paper describes wind tunnel tests performed on wind tunnel models of the Talavera de la Reina cable stayed bridge. The work describes the aeroelastic model construction and it is focused on the evaluation and analysis of the mean and peak wind loads at the tower foundation and the cable anchorages since these data can be very useful by the bridge manufacturer as a support for the bridge design. The work is part of a complete wind tunnel study carried out to analyze the aeroelastic stability of the bridge
Draft report Hawaii Deep Water Cable Program (HDWCP) : cable repair rationale
No full textThe Hawaii Deep Water Cable (HDWC) program has a major objective of determining the technical feasibility of deploying and operating, over a service life of thirty years, a submarine power transmission cable between Kohala on the island of Hawaii and the Makapuu area of Oahu. To this end the (HDWC) program has incorporated work elements to: 1) build and laboratory test a prototype cable that is designed to meet a wide range of environmental conditions expected in the route between the islands; 2) conduct at-sea tests to determine the feasibility of accurately laying a commercial cable with the proper tensions; and 3) perform bottom roughness surveys to establish the existence of acceptable cable laying routes and determine the laying requirements. Another task which this report addresses, is assessing the requirements for repairing the submarine portion of an inter-island cable system should damage occur during its operating life. The sections which follow discuss first the report prepared by Pirelli Cable Corporation, titled HDWC Program Repair Rationale which is included as Appendix A, and then develop a baseline approach to a repair scenario and a conceptual arrangement of equipment requirements integrated into the expected cable laying concept developed on other tasks of the HDWC program
A mathematical model for assessment of material requirements for cable supported bridges: implications for conceptual design
No full textRecent technological developments have led to improvements in the strengths of materials, such as the steel and wire ropes used in the construction of cable supported bridges. This, combined with technological advancements in construction, has encouraged the design of structures with increasing spans, leaving the question of material and environmental costs behind. This paper presents a refined
mathematical model for the assessment of relative material costs of the supporting structures for
cable-stayed and cable suspension bridges. The proposed model is more accurate than the ones published to date in that it includes the self weight of the cables and the pylons. Comparisons of material requirements for each type of bridge are carried out across a range of span/dip ratios. The basis of comparison is the assumption that each structure is made of the same material (steel) and
carries an identical design load, q, exerted by the deck. Calculations are confined to a centre span of a three-span bridge, with the size of the span ranging from 500 m to 3000 m. Results show that the optimum span/dip ratio, which minimises material usage, is 3 for a cable-stayed (harp type) bridge, and 5 for a suspension structure. The inclusion of the self weight of cable in the analysis imposes limits on either the span, or span/dip ratio. This effect is quantified and discussed with reference to
the longest cable-supported bridges in the world completed to date and planned in the future
DEMAND PULL AND SUPPLY PUSH IN PORTUGUESE CABLE TELEVISION
No full textIn this paper a Vector Autoregressive Model is applied to the most representative Portuguese cable television operators, in order to obtain a dynamic analysis of the interactivity established between the supply and the demand of network services, through the strategy of vertical integration of services. The results reveal the existence of two driving forces in the Portuguese main cable networks, on the one hand, the supply push which contributes to the enhancement of the basic cable demand, and on the other hand, the demand pull which intensifies the introduction of new vertically integrated services. In the two case studies, it is also detected that vertical integration of services has a negative impact on the price of the basic cable television service.Cable Television, Vector Autoregressive Model, Cointegration.
Testing the Effectiveness of Regulation and Competition on Cable Television Rates
No full textRegulation of the cable television industry was marked by remarkable periods of deregulation, re-regulation, and re-deregulation during the 1980s and 1990s. Using FCC firm-level survey data spanning 1993 to 2001, we model and econometrically estimate the effect of regulation and competition on cable rates. Our calculations indicate that while regulation lowered rates for small system operators, it raised them for medium and large systems. Meanwhile, competition consistently decreased rates from 5.6 to 8.8 percent, with even larger declines during periods of regulation. Our results suggest that competition is more effective than regulation in containing cable prices.cable rates, regulation, competition
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